There is a need to anchor or moor boats, buoys, drilling rigs and any other form of water-craft, either permanently or temporarily, in a given position. Such need gives rise to problems by virtue of the fact that, dependent upon circumstances and location, it may become necessary to anchor or moor such craft in different types of holdings. In the past it has been found that an anchor which might be particularly suitable for use in one type or form of holding, as for example sand or mud, may not be as appropriate for another or different type of holding, as for example rock or coral. In accordance with the known art, therefore, it has been a practice to utilize a different form of anchor dependent upon the nature of the holding. There has previously not been available a multi-use, multi-purpose anchor.
In the result, then in order to achieve the best or optimum anchoring effect a different form of anchor would need to be employed dependent upon the nature of the holding. That requirement gave rise to problems, regardless of the size of the water-borne craft or the like to be anchored. For obvious reasons it would not be particularly efficient or practical to have a craft operator need to change the type of anchor being used dependent upon circumstances and the nature of the holding below the craft.
Again in accordance with the known art there has been a tendency for conventional anchors, if disturbed, to roll over and thereafter be disposed on the ocean/sea/river/lake bottom (or holding) incorrectly, in effect the wrong way up. Prior art anchors, when so disturbed, would tend to lay on their side and remain that way. Clearly when in such a configuration the efficiency of operation of the overall anchor can be expected to be seriously reduced. Furthermore, when in such a configuration there will be a tendency for the anchor to be dragged across the holding, giving rise to disturbance of sand, mud, dislodgment of rock, destruction of coral etc. Such can have a deleterious effect on the overall environment and, if the relevant craft is being used, for example, for purposes of angling or fishing, such a disturbance to the holding/ocean bottom is again undesirable.
Another problem/disadvantage associated with anchors in accordance with the known art has related to the tendency or possibility of such anchors inadvertently working their way free from the holding, regardless of the nature of such holding. Once an anchor works itself free from its holding then the vessel or craft associated therewith will thereafter be totally susceptible to the vagaries of the tides, weather, etc. This can be especially unfortunate if, for example, the crew or passenger(s) of a vessel or craft are not aware of the fact that the anchor has worked loose, as for example if they are sleeping or otherwise occupied. An unanchored vessel can drift alarmingly, dependent upon the tides and the prevailing weather conditions, leaving itself liable to beaching, being swept onto rocks or reefs, etc. In other words, one consequence of an anchor working itself free from its holding can involve significant danger to the occupants of the vessel or craft.
Anchors of this general type usually comprise, as major components, a base member made up of one or more flukes and a shank associated therewith. Generally speaking the base member or each fluke is in the form of a substantially flat, planar member having a large surface area. The base member includes a leading end, generally pointed or other than blunt, the intention being to have that leading end penetrate the holding. When such an anchor is totally embedded in the relevant holding, the pressure exerted by the material of such holding on the base member represents a major component of the holding power of the overall anchor.
In accordance with known practices the base member or each fluke of such an anchor may be formed from a metal plate (or the equivalent), and may also include a number of external ribs for increased stiffness or strength. The shank may be in the form of an elongate member which is attached, either fixedly or movably, adjacent the stern of the base member, the shank including, at the other free end thereof, means allowing for connection thereof to a mooring line, cable, chain or the like. Generally speaking the shank will be substantially coincident with a central longitudinal axis of the base member when the anchor is viewed from above. The function of the shank is to transmit force between the base member and the mooring line, chain or cable.
In general terms there can be said to exist two broad categories or types of anchors. The first category includes traditional or so-called swing shank anchors, which anchors include shanks which are substantially straight and will be rotatably secured to one or more flukes or to a base member, to allow the shank to pivot at least to a limited degree on either side of each fluke or the base member. With such an anchor, as the anchor itself is dragged along the sea floor or holding, one side of the base member or each fluke thereof will face downwardly, in other words towards the sea floor or holding. Once the leading end of the base member or each fluke thereof actually penetrates the holding, the shank may then swing to the alternate side. For such anchors, since either side of the base member or each fluke thereof can be facing in a downwards direction, the base member or each fluke thereof will be substantially symmetrical in shape.
A second category of anchors of this general type includes the modern or so-called fixed shank type of anchor. Therein each fluke, or the base member, has a defined top surface and underside, this by reason of the fact that the attitude of the shank itself is fixed relative to each fluke during operation, as distinct from being rotatable as with the aforementioned traditional type anchors. In such modern anchors the shank extends upwardly from the top surface of each fluke or the base member. In order to be able to penetrate the holding, anchors of this type must land on the sea floor or holding with each fluke or the base member sited underneath the shank and with the bottom side of each fluke or the base member itself resting on the surface of the sea floor or holding.
Regardless of which type of anchor is being employed, an important parameter for measuring performance is the holding efficiency, or the ratio of the holding power to the weight of the anchor itself. By reason of the fluke symmetry of traditional or swing shank type anchors, additional weight needs to be added to the overall anchor itself, thereby reducing holding efficiency. Fixed shank anchors, on the other hand, eliminate some of the redundant structure associated with traditional or swing-type anchors.
A drawback associated with prior art anchors has been an inherent poor control of roll and yaw instability, both before and after the anchor has fully penetrated the holding. Yaw, by definition, is the rotation of an anchor about an axis which is normal to the top surface of the fluke, whilst roll is defined as rotation about the central longitudinal axis of the fluke or base member itself. The majority of prior art anchors have had their shanks attached at or in the vicinity of the rear or stern of each fluke or the base member, at a location which is far behind the pressure centre of each fluke or the base member itself. In that regard the “pressure centre” is intended to refer to the point on the top surface of each fluke or the base member through which the resultant force due to soil pressure passes. By reason of the relative location of the pressure centre and the shank attachment point (to each fluke or the base member), the shank will be effectively pushing each fluke or the base member in a forward direction, thereby creating a degree of instability.
When the leading end of each fluke or the base member encounters any form of uneven loading, then the anchor will yaw. In that regard it should be understood that the forces acting on the leading end of an anchor which cause yaw will also cause rolling of that same anchor. As the anchor yaws, the shank becomes angled relative to the mooring line. When the yawing force acting on the leading end of each fluke or the base member is coupled with the component of the mooring line force on the shank itself, a roll moment is created.
The present invention seeks to overcome the problems and disadvantages associated with the prior art by providing an improved form of anchor which is light-weight when compared with prior art arrangements), efficient in its operation in terms of holding efficiency, adjustable for use in different holding conditions, allows for easy initial penetration of the holding, stabilizes against yaw and roll and is also environmentally friendly.
In accordance with the present invention, therefore, there is provided an improved anchor including: a base member, one end thereof constituting a leading end of said anchor and being adapted to assist in anchorage/embedding of said anchor within a given holding; and a shank member fixedly attached to said base member, said shank member being adapted, in use, to receive and releasably retain at least one anchor line, rope or cable, wherein said base member is of a delta shape or configuration when viewed in plan and with a vortex of said delta shape constituting said leading end of said anchor, and wherein said base member includes opposed respective first and second flukes, each of said flukes being substantially triangular in shape when viewed in plan, said opposed flukes being disposed at an angle to one another and being joined along a line which constitutes a central longitudinal axis for said base member, wherein each free edge of each fluke is other than blunt whereby to constitute a cutting, digging or scraping means for embedding said anchor.